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/*
* Copyright (C) 2009 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.collect;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Preconditions;
import java.util.List;
import javax.annotation.Nullable;
/**
* Implementation of {@link ImmutableList} with exactly one element.
*
* @author Hayward Chan
*/
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
final class SingletonImmutableList<E> extends ImmutableList<E> {
final transient E element;
SingletonImmutableList(E element) {
this.element = checkNotNull(element);
}
@Override
public E get(int index) {
Preconditions.checkElementIndex(index, 1);
return element;
}
@Override public int indexOf(@Nullable Object object) {
return element.equals(object) ? 0 : -1;
}
@Override public UnmodifiableIterator<E> iterator() {
return Iterators.singletonIterator(element);
}
@Override public int lastIndexOf(@Nullable Object object) {
return indexOf(object);
}
@Override
public int size() {
return 1;
}
@Override public ImmutableList<E> subList(int fromIndex, int toIndex) {
Preconditions.checkPositionIndexes(fromIndex, toIndex, 1);
return (fromIndex == toIndex) ? ImmutableList.<E>of() : this;
}
@Override public ImmutableList<E> reverse() {
return this;
}
@Override public boolean contains(@Nullable Object object) {
return element.equals(object);
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (object instanceof List) {
List<?> that = (List<?>) object;
return that.size() == 1 && element.equals(that.get(0));
}
return false;
}
@Override public int hashCode() {
// not caching hash code since it could change if the element is mutable
// in a way that modifies its hash code.
return 31 + element.hashCode();
}
@Override public String toString() {
String elementToString = element.toString();
return new StringBuilder(elementToString.length() + 2)
.append('[')
.append(elementToString)
.append(']')
.toString();
}
@Override public boolean isEmpty() {
return false;
}
@Override boolean isPartialView() {
return false;
}
@Override public Object[] toArray() {
return new Object[] { element };
}
@Override public <T> T[] toArray(T[] array) {
if (array.length == 0) {
array = ObjectArrays.newArray(array, 1);
} else if (array.length > 1) {
array[1] = null;
}
// Writes will produce ArrayStoreException when the toArray() doc requires.
Object[] objectArray = array;
objectArray[0] = element;
return array;
}
}
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